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query.go
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query.go
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package parser
import "bigpot/relation"
import "bigpot/system"
type CommandType int
const (
CMD_SELECT = iota
CMD_INSERT
CMD_UPDATE
CMD_DELETE
)
type RangeVar struct {
SchemaName string
RelationName string
}
type Expr struct {
ReturnType system.Oid
}
type Var struct {
Expr
VarNo uint16
VarAttNo uint16
}
type TargetEntry struct {
Expr *Expr
ResNo uint16
ResName uint16
ResJunk bool
}
type RteType int
const (
RTE_RELATION = iota
RTE_SUBQUERY
RTE_JOIN
RTE_VALUES
RTE_FUNCTION
RTE_CTE
)
type RangeTblEntry struct {
RteType RteType
/* for relation */
relid system.Oid
}
type Query struct {
CommandType CommandType
TargetList []*TargetEntry
RangeTables []*RangeTblEntry
}
type Parser interface {
Parse(query_string string) *Query
}
type ParserImpl struct {
query string
namespace []*RangeTblEntry
}
type ParserError struct {
msg string
location int
}
func (e ParserError) Error() string {
return e.msg
}
func parseError(msg string) error {
/* TODO: get stack */
return ParserError{msg: msg}
}
func (parser *ParserImpl) Parse(query_string string) *Query {
lexer := newLexer(query_string)
yyParse(lexer)
query := &Query{}
return query
}
func (parser *ParserImpl) transformStmt(node Node) (*Query, error) {
switch node.(type) {
default:
return nil, parseError("unknown node type")
case *SelectStmt:
return parser.transformSelectStmt(node.(*SelectStmt))
}
panic("unreachable")
}
func (parser *ParserImpl) transformSelectStmt(stmt *SelectStmt) (query *Query, err error) {
query = &Query{CommandType: CMD_SELECT}
err = nil
if err = parser.transformFromClause(stmt); err != nil {
return
}
if query.TargetList, err =
parser.transformTargetList(stmt.targetList); err != nil {
return
}
return
}
func (parser *ParserImpl) transformFromClause(stmt *SelectStmt) error {
for _, item := range stmt.fromList {
switch item.(type) {
default:
return parseError("unknown node type")
case *RangeVar:
rv := item.(*RangeVar)
rte := &RangeTblEntry{}
/* TODO: implement relation_open_rv() */
relation := RelationOpenRv(rv)
rte.relid = relation.RelId
/* TODO: make Alias and add it to namespace, not Rte */
parser.namespace = append(parser.namespace, rte)
}
}
return nil
}
func (parser *ParserImpl) transformTargetList(targetList []*ResTarget) (tlist []*TargetEntry, err error) {
for _, item := range targetList {
var tle *TargetEntry
tle, err = parser.transformTargetEntry(item)
if err != nil {
return
}
tlist = append(tlist, tle)
}
return
}
func (parser *ParserImpl) transformTargetEntry(restarget *ResTarget) (tle *TargetEntry, err error) {
tle = &TargetEntry{}
err = nil
tle.Expr, err = parser.transformExpr(restarget.val)
return
}
func (parser *ParserImpl) transformExpr(node Node) (expr *Expr, err error) {
switch node.(type) {
default:
return nil, parseError("unknown node type")
case *ColumnRef:
/* TODO: Explore namespace and transform to Var */
}
panic("unreachable")
}
func RelationOpenRv(rv *RangeVar) *relation.Relation {
rel := &relation.Relation{}
return rel
}